The present invention concerns optoelectronic sensors and in particular a line camera with a receiving optics and a lighting arrangement in the vicinity of the receiving optics. The lighting arrangement consists of several, linearly aligned light emitting diodes (LED) for illuminating a linear receiving area with anamorphic imaging optics. The linear receiving area is imaged by the receiving optics on a position resolving, linear light receiver.
Such optoelectronic sensors are part of the state of the art and are used, for example, for imaging an object as well as for reading optically readable codes.
Sensors with a common lighting arrangement employ LEDs for illuminating the receiving area. The LEDs have no light bundling components or collimator, so that a relatively large proportion of the light emitted by the LEDs does not even illuminate the receiving area, which is an inefficient use of the generated light.
It is also known to construct such sensors by bundling the light emitted by the LEDs with a beam former or light bundling element to more or less concentrate the light in the receiving area.
For purposes of the present invention and this disclosure, the term “light” should be understood to include all types of optical radiation, including but not limited to all light from ultraviolet and infrared light and beyond.
The efficiency of such simple illumination without light bundling elements is particularly low when the distance between the optoelectronic sensor and the receiving area is relatively large.
Optoelectronic sensors fitted with a light bundling element frequently encounter the problem that the light distribution in the receiving area, that is, the light illumination profile, is poor and insufficient for many applications. For example, a homogeneous light distribution is often not assured. It is further not possible or is very costly to generate an intended illumination profile, for example to compensate for a decrease in the peripheral illumination of the receiving area along the periphery of the receiving optics. Further problems are encountered with such sensors when the receiving objective and the LEDs for illuminating the receiving area are arranged along a common line. Although this provides the optoelectronic sensor with good focal depth, because the illumination and its receipt lie in a common plane, the receiving objective interrupts the LED line, which causes a non-homogeneous illumination profile in the receiving area.